Metallic ink composition and writing instrument containing same

ABSTRACT

Metallic ink compositions for use in capillary-action markers are provided. More particularly, a metallic ink composition includes a polar solvent, an encapsulated metallic pigment, and a resin component.

BACKGROUND

1. Field of the Invention

The invention relates generally to metallic ink compositions for use incapillary-action markers. More particularly, the invention relates to ametallic ink composition comprised of a polar solvent, an encapsulatedmetallic pigment, and a resin component.

2. Brief Description of Related Technology

Writing instruments capable of making written markings containingmetallic pigments are known. For example, valve-action markers capableof making written markings containing metallic pigments have beendeveloped. Typically, such valve-action markers utilize a spring-loadednib, which opens a valve to an ink reservoir when depressed (e.g.,against a writing surface), thereby allowing the ink to flow from theink reservoir to the nib.

Valve-action markers require more parts than conventionalcapillary-action markers, and consequently their manufacture is morecomplicated and costly. Additionally, valve-action markers areproblematic in that the metallic pigments tend to settle to the bottomof the ink reservoir when the valve-action markers are not in use.Therefore, the user often has to violently shake the marker prior tousing same in order to effect distribution of the metallic pigmentsthroughout the ink composition so as to ensure that the ink compositiondelivered to the marker nib contains sufficient amounts of metallicpigment to produce the desired visual effect. Moreover, the usertypically has no means to verify that the metallic pigment has beenadequately distributed throughout the ink composition without writingwith the marker because the marker barrel is opaque. The user must alsosubsequently depress the nib against a writing surface with sufficientforce to open the valve to the ink reservoir and allow delivery of theink composition to the nib as described above. Such forces can cause thenib to excessively wear such that any written markings produced usingthe same frequently become indistinct over time. In view of theforegoing, other means of delivering metallic ink compositions aredesired.

Conventional capillary-action markers typically contain a fibrous inkreservoir and a nib in fluid communication therewith. Such markerstypically include an ink composition having a low viscosity because theadhesive forces (between the ink composition and the channel walls ofthe reservoir and/or nib) must exceed the cohesive forces of the inkcomposition to permit movement of the composition by capillary-action.Incorporating metallic pigments (e.g., including various metallicpigments such as aluminum and bronze flakes) into the low viscosity inkcompositions used in capillary-action markers is often challengingbecause such metallic pigments tend to settle out of the inkcompositions as set forth above. Even when the metallic pigments areadequately suspended in the ink compositions, the marker's fibersfrequently undesirably “filter” the metallic pigments and become cloggedover time. Accordingly, over time, the marker can be rendered incapableof making written markings containing metallic pigments.

U.S. Pat. No. 6,120,590 to Miyamoto discloses a ball point pencontaining a water-based, thixotropic gel ink having metallic lustrouscolor. Such thixotropic gel inks, however, are too viscous to besuccessfully adapted for use in many writing instruments, includingconventional capillary-action markers.

Capillary action markers including inks containing metallic pigmentsare, however, known in the art. U.S. Pat. No. 7,135,507 to Sextondiscloses a capillary action marker containing an ink including anaqueous dispersion of a metallic pigment and a specifichydantoin-formaldehyde co-polymer film-forming resin, optionallytogether with one or more of a color agent, a pH-adjusting agent,anti-settling agent, or a preservative. Additionally, U.S. Pat. No.7,297,729 to Sexton discloses a capillary action marker containing anink including a nitro solvent, a film-forming resin, a pigment or dye,and optionally, a substrate wetting agent. Still further, U.S. Pat. No.6,402,412 to Sukhna discloses an aqueous ink for a capillary actionmarker including a permanent water-based binder, a colored pigmentedpermanent water-based dispersion of sub-micron particle size, analuminum dispersion of specific particle size, a humectant, asurfactant, an anti-settling additive, a preservative and a pH adjuster.Too frequently, however, capillary action markers containing known inkformulations do not deliver a substantially homogenous ink compositionfor a reasonable amount of time (much less so over the lifetime of theproduct) and tend to clog. Such problems are believed in part to beattributable to the density, size, morphology, and surface treatment ofthe metallic pigments often used in writing compositions.

Further, conventional metallic marker ink compositions often includeresins that have substantially hydrophobic domains. While such resinshave generally been necessary to facilitate metallic pigment deliveryfrom the marker capillary action ink delivery system, these resins (dueat least in part to their substantially hydrophobic domains) do notreadily dissolve in polar (in particular, alcohol) solvents andtherefore significantly non-polar solvents must be used. Unfortunately,the aggressive non-polar solvents used in these compositions have beenfound to swell and/or attack marker components made from inexpensivethermoplastics such as polypropylene and polyethylene. As a result, moreexpensive thermoplastic components manufactured from engineeringthermoplastics such as nylon need to be used to obtain capillary actionmarkers containing these conventional metallic ink compositions.

SUMMARY

The invention provides a metallic ink composition comprising a polarsolvent, a metallic pigment dispersed in the solvent, and a resincomponent dissolved in the solvent, wherein the metallic pigmentcomprises a metal particle encapsulated with a coating that issubstantially insoluble in the solvent and the coating comprises one ormore polar molecules.

In a related aspect, the invention provides a capillary-action markercomprising an ink reservoir and a porous nib in fluid communication withthe ink reservoir, the ink reservoir containing a metallic inkcomposition in accordance with the invention.

In another related aspect, the invention provides a method of making awritten mark with a metallic ink composition comprising the steps ofproviding a capillary-action marker comprising an ink reservoir and aporous nib in fluid communication with the ink reservoir, the inkreservoir containing a metallic ink composition in accordance with theinvention, and contacting the nib of the capillary-action marker to asubstrate surface to make a written mark.

Further aspects of the invention may become apparent to those skilled inthe art from a review of the following detailed description, taken inconjunction with the appended claims. While the invention is susceptibleof embodiments in various forms, described hereinafter are specificembodiments of the invention with the understanding that the disclosureis illustrative, and is not intended to limit the invention to specificembodiments described herein.

DETAILED DESCRIPTION

The invention provides a metallic ink composition comprising a polarsolvent, a metallic pigment dispersed in the solvent, and a resincomponent dissolved in the solvent, wherein the metallic pigmentcomprises a metal particle encapsulated with a coating that issubstantially insoluble in the solvent and the coating comprises one ormore polar molecules.

Surprisingly and unexpectedly, the present inventor found that deliveryof the polar solvent-based (e.g., alcohol-based) metallic inkcompositions from the marker to the substrate was significantly improvedby encapsulating the metal particles with a coating comprising one ormore polar molecules, even when resins that have substantiallyhydrophobic domains are not present in the ink compositions. Further,the metallic ink compositions are delivered from the marker to thesubstrate even when polar solvents, which do not necessitate the use ofexpensive engineering thermoplastics for the marker components, are usedas the predominate solvent in the metallic ink compositions. Thecombination of polar solvent and a metallic pigment encapsulated with acoating that is substantially insoluble in the polar solvent and thatcomprises one or more polar molecules has been found to be particularlyadvantageous in facilitating the delivery of a substantially homogeneousink composition containing a metallic pigment with the end result beingthat any written markings (made using a writing instrument, particularlya capillary action marker, containing a metallic ink compositionaccording to the invention) generally include aregular/uniform/homogeneous amount of metallic pigment andadvantageously demonstrate a desired decorative effect oversubstantially the entire lifetime of the product. Specifically, byproviding metallic ink compositions containing a metallic pigmentcomprising a metal particle encapsulated with a coating that issubstantially insoluble in the polar solvent and in which the coatingcomprises one or more polar molecules, the metallic ink compositions arecapable of priming the nibs of capillary action markers with metallicpigment such that unacceptable failure due to under-priming (which isbelieved to be attributable to the pigment becoming undesirably fixedwithin the fibrous ink reservoir because of undesirable interactionsbetween the metallic pigment and the ink reservoir fibers such thatlittle metallic pigment is delivered from the nib to the substrate whena written mark is attempted) is beneficially avoided. Because theaforementioned undesirable interactions are minimized, delivery ofmetallic ink including a regular/uniform/homogeneous amount of metallicpigment is advantageously observed over the life time of the product.

Without intending to be bound by theory, it is believed that polar sitesfound on uncoated/non-encapsulated metallic pigments increase formationof undesirable interactions between the metallic pigments themselves andalso between the metallic pigments and the ink reservoir fibersresulting in pigment aggregation and/or fixation within the fibrous inkreservoir. These phenomena have been observed even with metallicpigments treated/coated with fatty acids having non-polar hydrocarbonchains such as stearic acid and oleic acid, presumptively because thefatty acid molecules can be easily displaced from the metallic pigmentsurface, thereby exposing polar sites on the metallic pigment surfacewhich can cause formation of undesirable interactions within the inkreservoir fibers. It is also believed that encapsulating the metalparticles with a coating comprising one or more polar moleculesincreases the polarity of the metal particles. In view of the foregoing,encapsulating the metal particles with a coating comprising one or morepolar molecules would not be expected to reduce the problem ofundesirable fixation of the pigment within the fibrous ink reservoir andthus would not be expected to improve the delivery of the metallic inkcompositions. Surprisingly and unexpectedly, encapsulating the metalparticles with a coating comprising one or more polar molecules whereinthe coating is substantially insoluble in the polar solventsubstantially improves the delivery of the polar-solvent based metallicink compositions according to the invention.

The invention provides a capillary-action marker comprising an inkreservoir and a porous nib in fluid communication with the inkreservoir, the ink reservoir containing a metallic ink compositioncomprising a polar solvent, a metallic pigment dispersed in the solvent,and a resin component dissolved in the solvent, wherein the metallicpigment comprises a metal particle encapsulated with a coating that issubstantially insoluble in the solvent and the coating comprises one ormore polar molecules.

The invention further provides a method of making a written mark with ametallic ink composition in accordance with the invention, the methodcomprising: providing a capillary-action marker comprising an inkreservoir and a porous nib in fluid communication with the inkreservoir, the ink reservoir containing a metallic ink compositioncomprising a polar solvent, a metallic pigment dispersed in the solvent,and a resin component dissolved in the solvent, wherein the metallicpigment comprises a metal particle encapsulated with a coating that issubstantially insoluble in the solvent and the coating comprises one ormore polar molecules; and contacting the nib of the capillary-actionmarker to a substrate surface to make a written mark.

Ranges may be expressed herein as from “about” or “approximately” oneparticular value and/or to “about” or “approximately” another particularvalue. When such a range is expressed, another embodiment according tothe invention includes from the one particular value and/or to the otherparticular value. Similarly, when particular values are expressed asapproximations, but use of antecedents such as “about,” “at leastabout,” or “less than about,” it will be understood that the particularvalue forms another embodiment.

Resins

To provide a metallic ink composition suitable for delivery via amarking instrument (e.g., a capillary-action marker), a resin componentis included in the ink composition. In general, resins can have avariety of functions in the ink, for example, resins may be incorporatedfor pigment wetting within the liquid matrix, resins may be incorporatedso as to aid film formation as the ink transits from a liquid to aplastic state during solvent dry, and resins may be incorporated togenerate the adhesion generally required to bond pigments to varioussubstrates.

In the metallic ink compositions according to the invention, the resincomponent is typically included in an ink in a range of about 1 wt % toabout 20 wt %, about 2 wt % to about 16 wt %, about 3 wt % to about 12wt %, about 4 wt % to about 8 wt %, and/or about 5 wt %, based on thetotal weight of the ink composition.

Suitable resins must show adequate solubility in the ink compositionpolar solvent(s). As a result, resins components suitable for use in themetallic ink compositions according to the invention generally do notinclude substantially hydrophobic domains. In one aspect, the term“substantially hydrophobic” refers to a resin that is not fully solublein a polar solvent and typically will be based on the solubility of theresin in the solvent system used in the ink composition. Such resinswith substantially hydrophobic domains generally have a solubility inthe polar solvent of less than 3% and/or less than 1% by weight.Structurally, substantially hydrophobic domains comprise hydrocarbons,for example, straight-chain or branched alkyl, cycloalkyl, alkenyl,cycloalkenyl, and/or aryl groups comprising at least 10 carbon atoms.Resins lacking adequate solubility in the ink composition polarsolvent(s) generally have substantially hydrophobic domains comprising asignificant portion of the resin, for example, at least 30%, at least40%, and/or at least 50% by weight. Exemplary resins comprisingsubstantially hydrophobic domains include terpene resins such asSYLVAGUM™TR 105 resin (Arizona Chemical, Jacksonville, Fla.), styrenatedterpene resins such as SYLVARES™ ZT 105LT resin (Arizona Chemical,Jacksonville, Fla.), styrene-methylstyrene copolymer resins such asSYLVARES™SA 140 (Arizona Chemical, Jacksonville, Fla.), hydrocarbonresins such as BITONER C9 modified C5 Resin C-2100 and BITONERhydrogenated C9 resins (Bitoner, Qingdao, China), natural rubbers suchas isoprene resins, amber resins, alkyd resins, vinylidenefluoride/hexafluoropropylene such as VITON, and phenylene sulfideresins. Of course, these are merely representative of substantiallyhydrophobic resins and do not encompass each example thereof. Typically,the ink compositions of the invention are substantially free of resinscontaining substantially hydrophobic domains, e.g., the ink compositionscontain less than 0.50 wt. %, less than 0.20 weight percent, less than0.10 weight percent of such resins.

Suitable resins include resins that are amphiphilic. By possessing bothpolar and nonpolar domains, such amphiphilic resin components can, forexample, facilitate adhesion of the metallic ink compositions to avariety of surfaces, including both polar and nonpolar surfaces.Additionally, suitable resins typically demonstrate various otherbeneficial properties, including, but nut limited to, resistance toabrasion, chemicals, and environmental sources of damage such as light,heat and moisture.

Suitable resins include resins having number average molecular weights(Mn) in a range of about 500 Daltons to more than 1 million Daltons,about 1000 Daltons to about 100,000 Daltons, and/or about 2000 Daltonsto about 10,000 Daltons. The preferred number average molecular weightfor a given resin will depend on various factors, including the desiredadherence level and/or the desired final viscosity of the inkcomposition.

Suitable resins include, but are not limited to, one or more resinsselected from polyvinyl butyral resins, polyacrylic acid resins,styrene-acrylic acid resins, polyamide resins, shellac resins, terpenephenolic resins, ketone-aldehyde condensation resins, polyurethaneresins, polyester resins, and mixtures thereof. Suitable resins areavailable from Sekisui Chemical Co., Ltd. (Osaka, Japan), Kuraray Co.,Ltd. (Tokyo, Japan), BASF (Ludwigshafen, Germany), DSM NeoResins(Waalwijk, The Netherlands), Xi'an Aladdin Biological Technology Co.,Ltd. (Shaanxi, China), Arizona Chemical Company (Jacksonville, Fla.),and Evonik Industries AG (Essen, Germany). Exemplary commerciallyavailable resins include, but are not limited to, BL-2 polyvinylbutyralresin (Sekisui Chemical Co, Ltd.), B-30H polyvinylbutyral resin (KurarayCo., Ltd.), JONCRYL 682 or JONCRYL 67 styrene-acrylic acid resin (BASF),NEOCRYL N819 polyacrylic acid resin (DSM NeoResins), VERSAM1D 759polyamide resin (BASF), shellac resin (Xi'an Aladdin BiologicalTechnology Co., Ltd.), TP300 terpene phenolic resin (Arizona ChemicalCompany), VARIPLUS TC ketone-aldehyde condensation resin (EvonikIndustries AG), SILICOPUR polyurethane resin (Evonik industries AG), andVESTICOAT UB polyester resin (Evonik Industries AG).

Metallic Pigments

A metallic pigment is included in the metallic ink compositionsaccording to the invention so as to provide a shimmering, sparkle, orglitter effect (i.e., art effect produced by the multi-directionalreflection of light).

Surprisingly and unexpectedly, encapsulating metal particles with acoating that is substantially insoluble in the metallic ink compositionsolvent and that comprises one or more polar molecules has been found tobe particularly significant for obtaining consistently enhanced writingperformance of capillary action markers comprising a polar solvent-basedmetallic ink composition according to the invention. For example, when ametallic ink composition comprises an uncoated/non-encapsulated metallicpigment (i.e., the metallic pigment is not a metallic pigment comprisinga metal particle encapsulated with a coating which comprises one or morepolar molecules and is substantially insoluble in polar solvent), but ispolar-solvent based and is otherwise prepared according to theinvention, a capillary action marker comprising said metallic inkcomposition eventually delivers little to no metallic pigment to asubstrate even though a significant amount of ink composition remainstherein. Without intending to be bound by theory, such markers arebelieved to deliver little to no metallic pigment because the metallicink pigment is undesirably interacting with the fibers of the inkreservoir such that it becomes fixed within the reservoir. The endresult is a written trace with a low density of the metallic pigment.

The metallic pigment component comprising a metal particle encapsulatedwith a coating according to the invention advantageously functions toassist in delivery of the metallic pigment as the ink composition of theinvention is drawn to the nib from the fibrous ink reservoir viacapillary-action and dispensed upon marking (e.g., making a writtenmarking with the ink composition of the invention). Thus, encapsulationof the metal particles with a coating promotes delivery of the metallicpigment from the capillary-action marker and is surprisingly able toeffect such delivery when the coating is substantially insoluble in themetallic ink composition polar solvent and the coating comprises one ormore polar molecules, even when resins that have substantiallyhydrophobic domains are not included in the metallic ink composition.

Suitable metal particles include, but are not limited to, metalparticles capable of functioning as pigments such as metal particlescomprising copper, zinc, aluminum, bronze, mica, oxides thereof,anodizes thereof, and combinations of any of the foregoing. Theaforementioned metal particles are encapsulated with a coating to obtainthe metallic pigments of the invention. The coating is substantiallyinsoluble in the solvent of the metallic ink composition and the coatingcomprises one or more polar molecules.

As used herein, the term “substantially insoluble in the solvent” refersto a solubility of the coating of the pigment particles in the inkcomposition solvents(s) that is typically less than 1 mg/mL, forexample, less than 0.5 mg/mL, less than 0.2 mg/mL, less than 0.1 mg/mL,less than 0.05 mg/mL, less than 0.01 mg/mL, and/or most preferably lessthan 0.001 mg/mL. Such insolubility can be confirmed using standardsolubility testing techniques, for example, by weighing a given amountof pigment particles before and after introduction into a given amountof polar solvent. For convenience, and because the metallic pigments areknown to be completely insoluble in polar solvents such that the onlycomponent that can dissolve is the coating itself, the parameter ismeasured relative to the weight of the pigment particles. Other methodsfor confirming insolubility include measuring the refractive index ofthe pigment before and after exposure to the solvent.

As used herein, the term “polar molecule” refers to a molecule that hasa nonzero dipole moment. Polar molecules typically have a dipole momentof at least 0.5 debye, at least 1 debye, at least 1.5 debye, at least 2debye, at least 3 debye, at least 4 debye, and/or at least 5 debye.

Suitable coatings include, but are not limited to, coatings comprisingmetal oxides and/or coatings comprising organic polymers. Preferredmetal oxide coatings include, but are not limited to, coatingscomprising silicon dioxide, alumina oxide, tin oxide, and/or titania.Such coatings may be translucent, but translucency is not required sincethe thickness of the coating typically is not great enough to mask theunderlying reflective surface of the metallic pigment. Preferred organicpolymer coatings include, but are not limited to, coatings comprisingurea-aldehyde polymer resins (e.g., urea-formaldehyde resins) and alkyl-and aryl-substituted derivatives thereof, such as methylurea-formaldehyde resins, phenyl urea-formaldehyde resins, and the like.Other suitable examples include the condensation products of urea withaldehydes such as acrolein, butyraldehyde, formaldehyde,paraformaldehyde, methylhemiformal, butylhemiformal, formaldehyde sodiumbisulfite adduct, glyoxal, acetaldehyde, benzaldehyde, furfural,phthalaldehyde, and terephthaldehyde. Suitable polymer resins typicallycontain polar functional groups such as hydroxyl, carboxyl, amino,ester, amide, ether, and the like.

Suitable metallic pigments encapsulated with a coating are availablefrom a number of pigment manufacturers such as, for example, SchlenkMetallic Pigments GmbH (Roth, Germany), Eckart GmbH (Hartenstein,Germany), Silberline Manufacturing Co., Inc. (Tamaqua, Pa.), and Paist(Huizhou, China). The metallic pigment particles are typically initiallyprovided in powder form (rather than as a paste) so as to providegreater control over the formulation. Of course, pastes can also beused.

Representative commercially available metallic pigments encapsulatedwith a coating comprising polar molecules and which is substantiallyinsoluble in the (polar) solvent include, but are not limited to,AQUAMET or POWDAL series silicon dioxide-coated aluminum pigments(Schlenk Metallic Pigments GmbH), STAPA HYDROLAN silicon dioxide-coatedaluminum pigment (Eckart GmbH), SILO-WET 651 silicon dioxide-coatedaluminum pigment (Silberline Manufacturing Co., Inc.), Noah's ArkW-series silicon dioxide-coated aluminum pigments (Paist), GRANDALurea-aldehyde resin-coated aluminum pigments (Schlenk Metallic PigmentsGmbH), ANNUAL RING R-series urea-aldehyde resin-coated aluminum pigments(Paist), CONSTANT silicon dioxide-coated pigments such as AQUADOR COPPERsilicon dioxide-coated bronze pigment (Schlenk Metallic Pigments GmbH),and CONSTANT silicon dioxide-coated pigments such as CONSTANT 2280/NRICH GOLD silicon dioxide-coated bronze-zinc pigment (Schlenk MetallicPigments GmbH). While the foregoing metallic pigment examples typicallyhave satisfactory particle diameters for use in capillary-action markerscontaining a metallic ink composition according to the invention, itshould be noted that other metallic pigments can be processed, e.g., wetsieved, to control/reduce their particle sizes in order to furtherenhance the performance of a capillary-action marker containing same.

In one aspect, aluminum metal particles encapsulated with a coatingwhich is substantially insoluble in a polar solvent and comprises one ormore polar molecules are used as the metallic pigment. In anotheraspect, bronze metallic pigments comprising copper/zinc alloy particlesencapsulated with a coating which is substantially insoluble in a polarsolvent and comprises one or more polar molecules are used as themetallic pigment. Of course, other elements such as nickel, lead,manganese, phosphorus, and silicon can also be included in thecopper/zinc alloy of the bronze pigments. In bronze metallic pigmentscomprising copper/zinc alloy without any additional elements, the weightratio of copper to zinc can be suitably varied between about 50:50 andabout 95:5, for example, about 90:10, between about 55:45 and about90:10, between about 60:40 and about 80:20, for example, about 70:30, toprovide “goldbronze” metallic pigments.

The metallic pigment typically has a density of from about 2.5grams/cubic centimeter (g/cc) to about 12.5 g/cc, about 4 g/cc to about11 g/cc, and more typically from about 6 g/cc to about 10 g/cc at 20° C.

Preferably, the metallic pigment has a substantially planar morphology.Such substantially planar metallic pigments are often referred to in theindustry as being corn flakes, silver dollars, or vacuum metalizedpigments. Substantially planar metallic pigments are extremely thintypically having a thickness between about ⅕^(th) and about 1/250^(th)and/or between about 1/10^(th) and about 1/100^(th) of the particlediameter. Generally, the substantially planar metallic pigments have anaverage thickness from about 0.01 microns to about 1 micron, about 0.05microns to about 0.50 microns, and/or about 0.08 microns to about 0.20microns. Typically, the substantially planar metallic pigments have anaverage thickness of less than about 0.50 microns, less than about 0.25microns, and/or less than about 0.10 microns.

The average dimensions of the pigment particles can be ascertained byperforming scanning electron microscopy (SEM). Typically, the pigmentshave an average diameter of from about 0.5 microns to about 12 microns;preferably, the pigments have an average diameter from about 1 micronsto about 10 microns; even more preferably, the pigments have an averagediameter from about 5 microns to about 9 microns, for example, from 6microns to about 8 microns. These sizes are generally preferred in theinks according to the invention in as much as such metallic pigmentshave demonstrated minimized settling in a capillary-action marker systemover time, and also do not clog the nib such that the dispensation ofthe ink from a capillary-action marker is interrupted.

In general, the largest dimension of the pigment particles is limited bythe need for the pigment particles to pass through the capillarychannels in the porous nibs and fibrous reservoirs of capillary actionmarkers and by the requirement that the pigment particles form stablesuspensions that do not settle over time. The smallest dimension of thepigment particles is generally selected to limit penetration of theparticles into the interstices of the intended substrate material assuch penetration can diminish the intended decorative effect.

Typically, a metallic pigment is included in the ink composition in anamount of about 5 wt % to about 40 wt %, about 7.5 wt % to about 35 wt%, about 10 wt % to about 30 wt %, about 12.5 wt % to about 25 wt %,about 20 wt %, about 5 wt % to about 30 wt %, about 5 wt % to about 25wt %, about 5 wt % to about 20 wt %, about 5 wt % to about 15 wt %,and/or about 10 wt % based on the total weight of the ink composition.

Solvent(s)

A polar solvent is included in the metallic ink compositions to dissolvethe resin component and to provide a continuous phase vehicle for thedispersed metallic pigments.

Surprisingly and unexpectedly, metallic ink compositions according tothe invention are delivered to the substrate from markers loaded withmetallic pigments comprising metal particles encapsulated with a coatingcomprising polar molecules even when polar solvents are used as thepredominate solvent in the metallic ink compositions. As a result, useof aggressive non-polar solvents in the metallic ink compositions can beavoided, advantageously allowing marker components for markers loadedwith the metallic ink compositions to be made from less expensivethermoplastics such as polypropylene and polyethylene.

Generally, the polar solvent comprises an organic solvent. The polarsolvent generally does not contain substantial amounts of water, e.g.,the solvent generally contains less than about 10 wt % water, preferablyless than about 5 wt % water, more preferably less than about 1 wt %water, and even more preferably less than 0.1 wt % water. Additionally,while aromatics may be included, for example to enhance the solubilityof selected resin components, the ink composition generally does notcontain substantial amounts of aromatics, e.g., the ink compositiongenerally contains less than about 5 wt % aromatics, more preferablyless than about 1 wt % aromatics, and even more preferably less than 0.1wt % aromatics.

Suitable polar solvents include polar protic and polar aprotic solvents.The polar solvent generally is present in an amount of about 30 wt % toabout 95 wt %, about 40 wt % to about 90 wt %, and/or more preferablyabout 55 wt % to about 85 wt %, based on the total weight of the inkcomposition.

In one aspect, the polar solvent comprises a polar protic solvent, forexample, one or more alcohol solvents. Suitable alcohol solvents includeone or more C1 to C15 alcohols, such as C2 to C10 alcohols, and/or C2 toC5 alcohols. The alcohol solvent can be a straight chain alcohol, abranched alcohol, a cyclic alcohol, or a mixture of the foregoing.Representative alcohol solvents include, but are not limited to,ethanol, propanol (e.g., isopropanol and/or n-propanol), butanol (e.g.,isobutanol and/or n-butanol), pentanol (e.g., isopentanol and/orn-pentanol), hexanol, and mixtures thereof. Other suitable proticsolvents include monoalkylated polyethers such as dipropyleneglycolmonoether.

In one aspect, the solvent comprises an polar aprotic solvent.Representative aprotic polar solvents include, but are not limited to,dimethylsulfoxide, dimethylacetamide, dimethylformamide, formamide,N-methylpyrrolidinone, N-methyl morpholine, propylene carbonate,ethylene carbonate, acetonitrile, esters such as ethyl acetate, ketonessuch as methylisobutylketone (MIBK) and acetone, tetrahydrofuran,cyclohexanone, toluene, and mixtures thereof. Combinations of polarprotic and polar aprotic solvents, including the polar protic and polaraprotic solvents specifically mentioned above, are also contemplated.

Marker Assemblies

The marker includes an ink reservoir disposed in a housing or barrel.The ink reservoir is in fluid communication with a porous nib. Thebarrel is typically seated by a plug, which helps to keep the inkreservoir in place.

Typically, the ink reservoir and the nib are disposed in such a mannerrelative to each other that the ink composition can be transferred fromthe ink reservoir to the nib via migration as a result of the inkreservoir being in fluid communication with the nib. The ink compositiongenerally moves by capillary-action within the reservoir, i.e., the inkcomposition generally moves by capillary-action from the distal end ofthe reservoir to the reservoir end which is proximate to the nib.Similarly, the ink composition generally moves within the nib bycapillary-action, i.e., the ink composition generally moves bycapillary-action from the portion of the nib which is proximate to thereservoir to the portion of the nib which is applied to a substrate tomake a written mark. Loading and priming of the ink reservoirs and thenibs, respectively, can advantageously be carried out over a widetemperature range from about 0° F. to about 77° F.

According to a preferred embodiment, the ink reservoir is a wick-typereservoir, and the fibrous nib is in continuous (i.e., permanent)contact therewith. In one embodiment, the coupling zone provides a largesurface area for the migration of a metallic ink composition from thereservoir to the nib (relative to the size of the nib). The couplingzone on the reservoir is usually at least about the same, at least about1.5 times greater than, and/or at least about 2 times greater than thecorresponding greatest diameter of the nib.

Capillary-action markers useful for delivering ink compositionscontaining metallic pigment particles comprise ink reservoirs having arelatively open structure. Suitable reservoirs for use in the markersaccording to the invention preferably have a reservoir fiber densityless than about 0.50 g/cc, more preferably less than about 0.25 g/cc.and most preferably less than about 0.10 g/cc.

The reservoir fibers can be manufactured from thermoplastic polymerssuch as, for example, polyesters, nylons, and mixtures thereof (providedthat the fibers are insoluble in the ink composition). The fibers insidethe reservoir can be linearly-oriented or entangled. To maintain theintegrity of the ink reservoir, the reservoir may be wrapped with asheet of polypropylene or high density polyethylene. Surprisingly, notonly are nylon wraps unnecessary, they can be undesirable. In certaininstances, nylon wraps have been found to detrimentally affect theperformance of markers according to the invention, for example, bycausing the markers to leak. The reservoirs can be of any dimensions aslong as the dimensions are sufficient for storing a predetermined amountof ink and for permitting the reservoir to fit into the desired markerbody or housing.

The nibs should be sufficiently porous to allow the metallic pigmentparticles to pass freely therethrough. The nib also should prevent inkcompositions from leaking when the nib is downwardly disposed. Fibers ofthe nib should be compatible with (i.e., insoluble in) the inkcomposition solvent system and capable of retaining the ink composition.Suitable nib fibers can be manufactured from thermoplastic polymers suchas, for example, polyesters, acrylics, nylons, and combinations thereof.

Methods of Preparing and Additives

A metallic ink composition according to the invention can be prepared bystandard methods. Generally, a metallic pigment is dispersed in asolvent, the resin is dissolved in a solvent and additional solvent canbe added to adjust the ink composition viscosity. A capillary-actionmarker containing the inventive ink composition can then be preparedaccording to standard processing methods.

The viscosity of the metallic ink composition at 25° C. is usually lessthan about 40 centipoises (cps), less than about 25 cps, and/or lessthan about 10 cps, for example, about 1 cps to about 40 cps, about 1 cpsto about 25 cps, about 1 cps to about 10 cps, about 1.5 cps to about 5cps, for example, about 2 cps. However, the ranges provided above canshift higher or lower, depending on the nature and porosity of the nibsand the fiber density of the ink reservoirs used in the markersaccording to the disclosure.

The ink may optionally contain other additives such as, for example,surface tension modifier(s), other synergic resin(s), surfactant(s),non-volatile solvent(s), co-solvent(s), dispersing agent(s),humectants(s), rheological additive(s), biocide(s) and other additivesknown in the art. These additives can be added to the ink compositionsin an amount such that the overall performance of the ink compositionsis not adversely affected in any aspect.

The ink compositions and writing instruments in accordance with thedisclosure can be better understood in light of the following examples,which are merely intended to illustrate the markers and ink compositionsand are not meant to limit the scope thereof in any way.

EXAMPLES

Metallic ink formulations 1 to 6 were prepared by combining theingredients identified in Table 1 in the amounts shown and mixing untila homogenous mixture was achieved. The ink compositions were then loadedinto markers equipped with an ink reservoir and a porous nib to obtainmetallic markers.

TABLE 1 Component (wt %) Function 1 2 3 4 5 6 Ethanol, SDA 3C, denaturedby Solvent 85  85  85  85  85  85  5% IPA (Nexon) AQUAMET 170 (SchlenkSilicon dioxide-coated 10  10  10  10  — — Metallic Pigments GmbH)Aluminum pigment CONSTANT 4117/N Pale Gold Silicon dioxide-coated — — —— 10  — (Schlenk Metallic Pigments Bronze pigment GmbH) METAGLOSS 1500(Schlenk Un-coated Aluminum — — — — — 10  Metallic Pigments GmbH)pigment (stearic acid- treated) Shellac R-49 (Xi'an Aladdin ShellacResin 5 — — — — — Biological Technology Co., Ltd.) JONCRYL 67 (BASF)Styrene-Acrylic Acid — 5 — — — 5 Resin VERSAMID 917 (BASF) PolyamideResin — — 5 — 5 — VARIPLUS TC (Evonik Ketone-Aldehyde — — — 5 — —Industries AG) Condensation Resin Color Intensity 5 5 5 5 5 2

The markers containing ink formulation 1 to 5 and comparative inkformulation 6 were used to make written marks on paper. Line/colorintensity of the marker was observed and rated on a visual scale of 1 to5, in which a score of 5 means a bright, opaque silvery line wasobserved and a score of 1 means the line was almost invisible. While notintending to be bound by any particular theory, it is believed that thelow color intensity score for comparative ink formulation 6 is due topigment fixation in the reservoir and/or nib of the marker, resulting ina reduced flow of pigment, low pigment transfer, and written lines oflow opacity and/or low brightness. The unacceptable performance of thismarker showed that replacing a coated pigment with anuncoated/non-encapsulated pigment significantly affected the capabilityfor delivering the metallic pigment particles from the marker. Incontrast, markers containing ink formulations 1 to 5 demonstrated thatmarkers containing ink compositions according to the invention providesuperior uniform delivery of the metallic ink compositions to thesubstrate, with no evidence of clogging of the nib.

What is claimed is:
 1. An ink composition comprising: (a) a polar,protic solvent; (b) a metallic pigment dispersed in the solvent; and (c)a resin component dissolved in the solvent, wherein the polar, proticsolvent is present in an amount of about 35 wt % to about 95 wt % basedon the total weight of the ink composition, the metallic pigmentcomprises a metal particle encapsulated with a coating that issubstantially insoluble in the solvent and the coating comprises silicondioxide and an organic polymer comprising a urea-aldehyde polymer resin,an alkyl- or aryl-substituted derivative of a urea-aldehyde polymerresin, or a condensation product of urea with an aldehyde.
 2. The inkcomposition of claim 1, wherein the solvent is an alcohol solvent. 3.The ink composition of claim 1, wherein the solvent comprises one ormore C1 to C15 alcohols.
 4. The ink composition of claim 1, wherein themetallic pigment comprises a metallic pigment selected from the groupconsisting of copper, zinc, aluminum, bronze, mica, oxides thereof,anodizes thereof, and combinations of any of the foregoing.
 5. The inkcomposition of claim 1, wherein the metallic pigment comprises aluminum.6. The ink composition of claim 1, wherein the metallic pigmentcomprises a copper/zinc alloy.
 7. The ink composition of claim 1,wherein the viscosity of the metallic ink composition at 25° C. is lessthan about 40 centipoises (cps).
 8. The ink composition of claim 1,wherein the metallic pigment has a substantially planar morphology. 9.The ink composition of claim 1, wherein the metallic pigment has anaverage thickness between about 0.01 microns to about 1 micron.
 10. Theink composition of claim 1, wherein the metallic pigment has an averagediameter between about 0.5 microns and about 12 microns.
 11. The inkcomposition of claim 1, wherein the metallic pigment is present in anamount between about 5 wt % and about 40 wt %, based on the total weightof the ink composition.
 12. The ink composition of claim 1, wherein theink composition has a total resin content between about 1 wt % and about20 wt %, based on the total weight of the ink composition.
 13. The inkcomposition of claim 1, wherein the resin component comprises one ormore resins selected from the group consisting of polyvinyl butyralresins, polyacrylic acid resins, styrene-acrylic acid resins, polyamideresins, shellac resins, terpene phenolic resins, ketone-aldehydecondensation resins, polyurethane resins, polyester resins, and mixturesthereof.
 14. The ink composition of claim 1, wherein the coatingcomprises an organic polymer comprises a urea-formaldehyde resin, aphenyl urea-formaldehyde resin, a methyl urea-formaldehyde resin,acrolein, butyraldehyde, formaldehyde, paraformaldehyde,methylhemiformal, butylhemiformal, formaldehyde sodium bisulfite adduct,glyoxal, acetaldehyde, benzaldehyde, furfural, phthalaldehyde, orterephthaldehyde.
 15. The ink composition of claim 1, wherein the inkcomposition is substantially free of resins containing substantiallyhydrophobic domains.
 16. The ink composition of claim 1, wherein thepolar solvent comprises a C2-C5 alcohol, and the metallic pigmentcomprises an aluminum particle encapsulated with a coating comprisingsilicon dioxide.
 17. A marker comprising: an ink reservoir and a porousnib, the ink reservoir containing an ink composition comprising ametallic ink composition comprising: (a) a polar, protic solvent; (b) ametallic pigment dispersed in the solvent; and (c) a resin componentdissolved in the solvent, wherein the metallic pigment comprises a metalparticle encapsulated with a coating that is substantially insoluble inthe solvent and the coating comprises silicon dioxide and an organicpolymer comprising a urea-aldehyde polymer resin, an alkyl- oraryl-substituted derivative of a urea-aldehyde polymer resin, or acondensation product of urea with an aldehyde.
 18. A method of making awritten mark, comprising: providing a capillary-action marker comprisedof an ink reservoir and a porous nib, the ink reservoir containing anink composition according to claim 1; and contacting the nib of thecapillary-action marker to a substrate surface to make a written mark.19. The ink composition of claim 1, wherein the polar, protic solvent ispresent in an amount of about 40 wt % to about 90 wt % based on thetotal weight of the ink composition.
 20. The ink composition of claim 1,wherein the coating consists of silicon dioxide.
 21. The ink compositionof claim 1, wherein the coating is in contact with the polar, proticsolvent.
 22. The marker of claim 17, wherein the ink reservoir iswrapped with a sheet comprising polypropylene density polyethylene. 23.The ink composition of claim 1, wherein the polar, protic solvent ispresent in an amount of about 55 wt % to about 85 wt % based on thetotal weight of the ink composition.
 24. The ink composition of claim 1,wherein the organic polymer consists of a urea aldehyde polymer.
 25. Anink composition comprising: (a) a polar, protic solvent; (b) a metallicpigment dispersed in the solvent; and (c) a resin component dissolved inthe solvent, wherein the polar, protic solvent is present in an amountof about 40 wt % to about 90 wt % based on the total weight of the inkcomposition, the metallic pigment comprises a metal particleencapsulated with a coating that is substantially insoluble in thesolvent and the coating comprises silicon dioxide and an organic polymercomprising a urea-aldehyde polymer resin, an alkyl- or aryl-substitutedderivative of a urea-aldehyde polymer resin, or a condensation productof urea with an aldehyde.
 26. The ink composition of claim 25, whereinthe solvent is an alcohol solvent.
 27. The ink composition of claim 25,wherein the solvent comprises one or more C1 to C15 alcohols.
 28. Theink composition of claim 25, wherein the metallic pigment comprises ametallic pigment selected from the group consisting of copper, zinc,aluminum, bronze, mica, oxides thereof, anodizes thereof, andcombinations of any of the foregoing.
 29. The ink composition of claim25, wherein the metallic pigment comprises aluminum.
 30. The inkcomposition of claim 25, wherein the metallic pigment comprises acopper/zinc alloy.
 31. The ink composition of claim 25, wherein theviscosity of the metallic ink composition at 25° C. is less than about40 centipoises (cps).
 32. The ink composition of claim 25, wherein themetallic pigment has a substantially planar morphology.
 33. The inkcomposition of claim 25, wherein the metallic pigment has an averagethickness between about 0.01 microns to about 1 micron.
 34. The inkcomposition of claim 25, wherein the metallic pigment has an averagediameter between about 0.5 microns and about 12 microns.
 35. The inkcomposition of claim 25, wherein the metallic pigment is present in anamount between about 5 wt % and about 40 wt %, based on the total weightof the ink composition.
 36. The ink composition of claim 25, wherein theink composition has a total resin content between about 1 wt % and about20 wt %, based on the total weight of the ink composition.
 37. The inkcomposition of claim 25, wherein the resin component comprises one ormore resins selected from the group consisting of polyvinyl butyralresins, polyacrylic acid resins, styrene-acrylic acid resins, polyamideresins, shellac resins, terpene phenolic resins, ketone-aldehydecondensation resins, polyurethane resins, polyester resins, and mixturesthereof.
 38. The ink composition of claim 25, wherein the organicpolymer comprises a urea-formaldehyde resin, a phenyl urea-formaldehyderesin, a methyl urea-formaldehyde resin, acrolein, butyraldehyde,formaldehyde, paraformaldehyde, methylhemiformal, butylhemiformal,formaldehyde sodium bisulfate adduct, glyoxal, acetaldehyde,benzaldehyde, furfural, phthalaldehyde, or terephthaldehyde.
 39. The inkcomposition of claim 25, wherein the ink composition is substantiallyfree of resins containing substantially hydrophobic domains.
 40. The inkcomposition of claim 25, wherein the polar solvent comprises a C2-C5alcohol, and the metallic pigment comprises an aluminum particleencapsulated with a coating comprising silicon dioxide.
 41. A method ofmaking a written mark, comprising: providing a capillary-action markercomprised of an ink reservoir and a porous nib, the ink reservoircontaining an ink composition according to claim 25; and contacting thenib of the capillary-action marker to a substrate surface to make awritten mark.
 42. The ink composition of claim 25, wherein the polar,protic solvent is present in an amount of about 55 wt % to about 85 wt %based on the total weight of the ink composition.
 43. The inkcomposition of claim 25, wherein the coating is in contact with thepolar, protic solvent.
 44. The ink composition of claim 25, wherein theorganic polymer consists of a urea aldehyde polymer.